Unoriented polyolefin filament with polyurethane foam core



Sept. 24, 968 J. c. I EwIs, IR 3,403,070

UNORENTED POLYOLEFIN FILAMENT WITH POLYURETHANE FOAM CRE Filed Jan. 3l, 1964 INVENTOR JOHN C. LEWIS, JR.

MORGAN,FINNEGAN,DURHAM a PINE ATTORNEYS United States Patent() 3,403,070 UNORIENTED POLYOLEFIN FILAMENT WITH POLYURETHANE FOAM CORE `Iohn C. Lewis, Jr., Middlebury, Vt., assigner to Polymers, Inc., Middlebury, Vt., a corporation of Vermont Filed Jan. 31, 1964, Ser. No. 341,704 5 Claims. (Cl. 161-175) ABSTRACT OF THE DISCLOSURE This invention relates to artificial filaments and more specifically to large hollow filaments made from unoriented polyolefin resins filled with a cellular-type foam useful as bristles and mop fibres. The cellular type foam forming the core of the filaments of this invention is a polyurethane foam composition.

For many years synthetic filaments have been produced in various cross-sectional shapes such as circular, square, tapered, X and Y and three-square from therrrnoplastic resins like polystyrene, polystyrene-acrylonitrile, polyvinylchloride, polyethylene, polypropylene and polyamides. Normally, these filaments are comprised of a single polymer composition and are highly oriented to irnpart to the particular filament the maximum physical properties; such properties being stiffness, recovery, abrasion resistance, wet and dry wear, heat distortion and the like. Many attempts have been made to create the perfect synthetic filament, the closest being an oriented polyamide. The polyamides, better known as nylons, are described in United States Patent 2,130,523 to W. H. Carothers. Of all the nylons, the condensation product from hexamethylene-diamine and sebacic acid proves to be the superior, and nylon filaments of this type have all the aforementioned physical properties and also display excellent chemical properties. However, the one great disadvantage of nylon filaments is cost, and even through nylon vfilaments made in different cross-sectional shapes seem to help the bulk density/ cost ratio, th'e cost per pound is still not advantageous.

Polypropylene filaments, on the other hand, fall into the low-cost category but have the tendency to suffer matting and permanent deformation. Also, polypropylene filaments lack good recovery. Certain attempts have been made to overcome this deformation, for instance, by controlling the degree of orientation, but oftentimes one good characteristic such as abrasion resistance is forfeited for tensile strength and elongation or vice versa. It also has been found true that polypropylene filaments having various cross-sectional shapes are no good from the recovery standpoint since any protruding webs or fins split and tear when the oriented filaments are bent through 180. It is therefore apparent that the only oriented filament possessing all the physical and chemical properties desired of a brush fibre is nylon, i.e., nylon 6-10.

Prior to this invention, unoriented filaments of the polyolefin type have been made such as those set forth in co-pending patent application 231,799, filed Oct. 19, 1962 now U.S. Patent No. 3,121,040 issued Feb. 11, 1964. Such filaments exhibit essentially complete recovery after deformation. The physical and chemical properties of such unoriented polyolefin filaments are directly comparable to nylon 6-10 filaments and markedly superior to nylon 6-10 filaments in maintaining their stiffness (wet and dry ratio) when exposed to wet or high humid conditions. Unoriented polyolefin filaments can be produced in various cross-sectional shapes and in hollow tubes down to diameters of 0.010" having wall thickness in the range of 3,403,070 Patented Sept. 24, 1968 ICC 0.001". Such filaments have excellent recovery and are low-cost fibres.

It has ybeen found that when using hollow fibres for certain applications such as applying abrasive slurries to surfaces, the hollow void tends to fill up with the slurry, but if the applicator rotates or moves too rapidly, the centrifugal force tends to eject the slurry rather than hold it. Also the slurry must be continually added to the operation as the slurry is always being discarded. When nylon type fibres are used in the presence of water slurries, they absorb a given amount of moisture and lose their stiffness. Therefore, if a light weight unoriented polyole- .tin fibre could retain all its dry stiffness in a wet application and also discharge during operating a constant amount of abrasive material, i.e., as it wears, it would eliminate the necessity for adding large quantities of water slurries. This would also eliminate high cost of maintenance and excessive wear of lmachine parts, as high concentrations of abrasive slurries tend to spill over onto machinery in such applications.

Another important area where hollow fibres are used is in connection with applications where liquids `are present and the hollow void has an effect of capillary action. While immersed in such liquid, the hollow fibre retains liquid, but when removed, it discontinues to hold the liquid.

Another area where light weight fibres .are used is in insulating and filling materials where the hollow void is supposed to act like a moisture barrier or in the case of filling materials, act like a resilient cushion. The hollow sections tend to collapse and deform and never return to their original shape, thus rendering the fibre useless.

Other objects yand advantages of this invention will be set forth in part hereinafter and in part will be obvious herefrom, or may be learned by practice with the invention, the same being realized and attained by means of the improvements pointed out in the :appended claims.

It is therefore an object of this invention to create a light weight synthetic filament having a highly desirable overall balance of properties.

Another object of this invention is to provide a lowcost synthetic filament having excellent recovery, a high stiffness ratio (wet or dry) and superior wearing qualities.

Still another object of this invention is to provide novel filaments which have insulating properties.

Yet another object of this invention is to provide synthetic filaments which can be used to absorb liquids.

In the drawings:

FIGURE 1 is a longitudinal sectional view of one embodiment of my invention consisting of an unoriented high pressure polyethylene shell with a core consisting of a polyester based-polyurethane foam.

FIGURE 2 is a transverse section of the filament of FIGURE 1.

FIGURE 3 is a longitudinal sectional View of a second embodiment of my invention consisting of an unoriented polypropylene shell with a core consisting of a polyester-based polyurethane foam in which an abrasive particle is held by the foam.

FIGURE 4 is a transverse section of the filament of FIGURE 3.

FIGURE 5 is a longitudinal sectional view of a third embodiment of my invention consisting of an unoriented polyallomer shell with a core consisting of a polyether based-polyurethane foam and having running longitudinally along its entire length a slice cutting into the annular wall and foam core.

FIGURE 6 is a transverse section of the filament of FIGURE 5.

It has been found that the objects of my invention may be realized by forming a fibre comprising an unoriented polyolefin outer shell of the type described hereinafter and an inner core of polyurethane foam, More particularly, the outer shell of the fibre of the present invention is an unoriented polyolefin hollow fibre of the type described in the aforementioned co-pending application Ser. No. 231,779, filed Oct. 19, 1962, and consists of annular walls Whose radius to annular wall thickness ratio is in the order of at least 4 to 1.

As indicated above, the outer shell is of a polyolen composition, such, for example, as high pressure polyethylene, polypropylene, polyallomer or physical and/ or chemical mixtures thereof. As indicated hereinabove, the inner core of the fibre of this invention is made of a polyurethane foam. The term polyurethane foam as used herein, includes both polyester based-polyurethane foam and polyether based-polyurethane foam. Any conventional polyester based-polyurethane foam or polyether basedpolyurethane foam may be used as the core material. As is Well known, polyester based-polyurethane foams are conventionally made by reaching an organic polyisocyanate, e.g., toluene diisocyanate, with a polyester containing free hydroxyl and/or carboxyl groups, e.g., the polyester resin reaction product of ethylene glycol and adipic acid. When reacting a polyisocyanate with an hydroxypolyester, a small amount of water is added to bring about carbon dioxide formation with polyisocyanate and the reaction is accelerated in known manner by the addition of catalysts, e.g., a tertiary amine catalyst such as triethylamine and N-methylmorphaline.

Polyether based-polyurethane foams are conventionally made in a manner similar to that described above except that in place of a polyester, a polyether, eg., is employed for reaction with the organic polyisocyanate. U.S. Patents 2,726,219, 2,814,606 and 3,029,209 disclose polyurethane foam compositions that may be used as the core material in accordance with this invention. The polyurethane foam core material is generally of the flexible or semi-rigid foam type so that the fibre exhibits the desired flexural characteristics.

In order to describe the invention more fully, specific reference will now be made to the drawings. FIGURES 1-6 illustrate preferred forms of the fibres in accordance with the invention, although such forms are given by way of example only, and other forms may be used. As shown in FIGURE 1, the fibre of this invention is comprised of an unoriented high pressure polyethylene shell 1 and a polyester based-polyurethane foam core 2. The outer shell or wall of the fibre consists of an annular wall as shown in FIGURE 2` whose radius R to annular wall thickness S ratio is in the order of at least 4 to 1.

In FIGURES 3 and 4 there is shown another embodiment yof my fibre comprising an unoriented polypropylene shell 3 and a polyester based-polyurethane foam core 4, containing foreign compounds or substances 5. Any foreign material can be incorporated physically or chemically to the foam as long as the material does not interfere with the processing of the foam. Such material can be fire retardant compounds, abrasive compounds, Watersoluble compounds, colorants or any organic or inorganic compound which allows for foam processing. The amount of the additive is not important as long as consistent cellstructure is maintained throughout the foam.

In FIGURES 5 and 6 there is shown another embodiment of my fibre comprising an unoriented polyallomer shell 6 and a polyether based-polyurethane foam core 7, said fibre having slit 8i running longitudinally along its annular Wall, cutting into the core and terminating at the center. This opening actually cuts into the cell-structure of the foam, thus allowing air or liquids to enter into the hollow voids of the foam. The amount of void per Kcell, or absorbency per cell unit is controlled by the chemical composition formula and/or method of processing.

In the specific embodiments of filaments described hereinbefore, any convenient processing technique may be used` for -filling the unoriented polyolefin outer shell with polyurethane foam. A procedure which may be used is as follows:

First, a polyurethane premix is formed by blending an appropriate amount of polyester (or polyether) resin with appropriate amounts of catalyst and water. If the desired foam is to include a foreign substance, it may be incorporated in the premix. To this premix is added an appropriate amount of organic polyisocyanate and the resulting composition is mixed thoroughly to form a foam-producing mix. Immediately after, samples of hollow unoriented polyolefin fibres are immersed in the aforementioned foam-producing composition to a sufficient depth and suction is applied to the projecting ends of the fibres to cause the foam-producing mix to travel up into the hollow portion of the fibre. In a matter of seconds, the foaming reaction starts and the cell structure begins to foam. Within a relatively short period of time, e.g., 30 seconds, the hollow portion of the fibers are completely filled with polyurethane foam.

In order to illustrate the aforedescribed procedure more specifically, the following specific example is now given:

A batch of 2 pounds per cubic foot flexible polyurethane foam was made by the following recipe (all reactants Were at room temperature):

100 grams of Formez-50 (a polyester-resin) was blended with 2 grams of N-ethyl morpholine in an electric mixer for 45 seconds and then 3.6 grams of distilled water was added and the mixture allowed to mix for another 30 seconds. To this resin premix, 105 grams of Nacconate (80:20 mixture of 2.4 and 2.6-toluene diiocyanate) was added and mixed for approximately 10 seconds and then poured intoV a paper cup.

Immediately after, 10 inch samples of polypropylene fibres, (hollow) measuring 0.050" in diameter and having a 0.003 annular wall thickness, were immersed in the foam mixture to a depth of 1/2 inch and a slight vacuum was applied to the projecting ends of the fibres, which allowed the foam mix to travel up into the hollow portion of the fibre. Soon after, that is, 5-10 seconds, the foaming reaction started and the cell structure began to form. Within 30 seconds the hollow portion of the fibres were completely filled with polyurethane foam.

The laments of this invention may be made in long continuous lengths or cut into shorter lengths and used for bristles, fibres and the like. They may be tapered if so desired.

Likewise, the filament can be made in the Wide Variety of sizes. The filament can have an overall cross-sectional dimension from about 0.010 to 0.500 of an inch, and the cross-section area of the core portion comprising at least 60% of the total cross-sectional dimension.

By proper core design, the fibre can be made to wear down at different rates, and exposing to the wearing surface at all times definite amounts of abrasive material. In a like manner, if the core is designed =for liquid retention, by selection of proper cell-size, the fibre will retain its maximum quantity of liquid.

The filaments of this invention may be used to prepare improved products such as: mops, polishing brushes, abrasive strip-brushes, rotary brushes, liquid retention brushes, fabrics, insulating mats, etc.

Colorants, extenders, plasticizer, catalysts and modifiers may be added to these materials as practice dictates.

What is claimed is:

I. A synthetic filament comprising an unoriented polyolefin shell whose radius to annular wall thickness ratio is in the order of at least 4 to 1, and an inner core of a polyurethane foam composition.

2. A synthetic filament according to claim 1 in which the outer shell is made of high pressure polyethylene.

6 References Cited UNITED STATES PATENTS 3,121,040 2/1964 Shaw et al. 16l-18l 5 ROBERT F. BURNETT, Primary Examiner.

L. M. CARLIN, Assistant Examiner. 

